1. Field of the Invention
The present invention relates to a flexible substrate processing apparatus.
2. Description of the Related Art
In recent years, graphene, which is one of carbon materials, has attracted attention as an electronic material with high conductivity, high flexibility, and high mechanical strength, and attempts have been made to apply graphene to a variety of products.
Application of graphene to power storage devices such as a lithium secondary battery and a lithium-ion capacitor is one of the attempts. Graphene which coats or is mixed into an electrode of the power storage device can increase the conductivity of the electrode.
As an example of a method for forming graphene, the method of reducing graphite oxide in the presence of a base is disclosed in Patent Document 1. In order to form graphite oxide, a method using sulfuric acid, nitric acid, and potassium chlorate as an oxidizer, a method using sulfuric acid and potassium permanganate as an oxidizer, a method using potassium chlorate and fuming nitric acid as an oxidizer, or the like can be employed.
A solution containing graphite oxide which is formed by the above method is subjected to ultrasonic treatment or is stirred, whereby the graphite oxide is separated to form graphene oxide. Then, the graphene oxide is reduced in the presence of a base, so that graphene can be formed.
Alternatively, the graphene oxide can be reduced by heat treatment to form graphene.